Keeping Sepia bandensis
Keeping Sepia bandensis – The Dwarf Cuttlefish
I’ve long considered myself a “fish guy,” but after a month working with Sepia bandensis, the Dwarf Cuttlefish, I must admit I’ve never seen, let alone kept, a more amazing marine animal than this remarkable mollusk. Despite its name, this little critter is not a fish at all but a cephalopod, closely related to octopus and squid. They’ve been described by cuttle pioneer Richard Ross of the Steinhart Aquarium as looking like little UFO’s zipping around the tank. And of all the animals that may be kept in tropical saltwater aquaria, Sepia bandensis is a most fascinating and rewarding species in so many different ways. They are visually stunning animals with the ability to change color, pattern and texture in the blink of an eye. They are perfect predators, like tiny raptors of the sea as they swoop down and snag their prey with their lightening-fast feeding tentacles. They are intelligent, interacting with their keeper and each other in subtle and dramatic ways. And at only 3-4″ long when mature, they’re small enough to make housing them a real possibility for expert hobbyists as well as public aquariums.
Like the other cephalopods, Sepia bandensis possess an array of amazing adaptions that make them one of the most unique animal groups in the marine world. Perhaps most amazingly, they can change color and pattern in the blink of an eye from a blanched white resting color to near jet black when they’re excited and every shade and pattern in between. They can even scroll bands of color across their bodies, an effect which some have suggested is used to mesmerize prey as well for intraspecies communication. They achieve these amazing effects through the use of specialized pigment cells commonly referred to as chromatophores but which are actually cells of 3 different types, each of which has its own unique role in creating the colors and patterns for which this group is so well known. Chromatophores produce the basic colors in a range from off-white through beiges and browns and finally to a near jet black. Iridiphores produce iridescent blues and greens which can be particularly visible around the fin of S. bandensis. And leucophores, which are white, scatter light to help the animal blend into its surroundings. In addition to color and pattern changes, these little cuttles can produce a texture like tags or folds of skin which further aids their ability to camouflage. Like the color changes, these textural changes happen in an instant. The speed and complexity of the color and texture changes of cephalopods and especially cuttlefish like Sepia bandensis surpass those of any other animal group, including some fish like flasher wrasses and even chameleons which have become the archetypal color change experts in the animal world.
Beyond their amazing skin, S. bandensis has a number of other unique physical attributes and adaptations that they share with their cephalopod cousins including 3 hearts, a ring-shaped brain, copper-based blood (it’s blue!), jet propulsion, 360 degree vision and the ability to squirt ink (the fact that they share their genus name with a type of ink is no accident.) They also have mouths with a sharp beak and a rasping radula for a tongue, both of which they share with octopus and squid. They have 8 arms arranged around their mouth as well as two feeding tentacles which they can fire with amazing speed and accuracy. In addition to their ability to swim with jet propulsion via their excurrent syphon, they can cruise around more slowly and nimbly using undulations of a lateral fin that girds their mantle. Inside this mantle is their cuttle bone, an incredibly light and porous calcium structure used to regulate buoyancy and often sold in pet stores as a calcium supplement for captive birds. Finally, these crazy critters can actually walk across the bottom using two of their arms and two skin flaps on the bottom of their mantle.
Here we see a pair S. bandensis displaying two of the most recognizable of their myriad awesome behaviors; “walking” and scrolling bands of color across their bodies.
The range of Sepia bandensis includes island groups in the southwest Pacific Ocean where they are typically found in shallow waters over coral and sand and where they are most active at night.
S. bandensis are ambush predators, blending in with their surroundings and waiting until an unsuspecting fish or crustacean ventures too near and then firing those feeding tentacles with blinding speed to snare their next meal. And they are short lived animals with fairly high reproductive rates, both of which factor heavily into their captive care to which we will now turn our attention.
For any person or institution considering keeping Sepia bandensis in captivity, a number of issues need to be considered and accounted for and I will attempt to address the basics of those issues here. This article does not attempt to cover all possible ways to successfully keep the dwarf cuttle, but will focus on one successful effort where a breeding population has been kept in holding and display tanks for nearly two years. And this author does not suppose to be an expert in the maintenance of dwarf cuttles but a student anxious to share information gleaned over a month-long stint as one of the aquarists primarily responsible for the care of this captive population.
No one should consider keeping S. bandensis who has not successfully kept a marine reef tank for at least a couple of years. These animals are not supremely difficult, but they do require the rather rigorous parameters of a reef tank in terms of temperature, salinity, pH and nutrient levels. They also require twice-daily feedings by hand or via feeding stick of a variety of frozen crustaceans. And, finally, if you’re keeping at least one male and female and you would like to have these animals in your care for more than just one year, you must be able to care for eggs and babies at various stages of development. We’ll address the basics of these three areas of their care, housing, feeding and rearing of the offspring, in the following three sections.
As was mentioned above, basic reef tank water parameters are appropriate for a Sepia bandensis tank. This means temps in the range of 74 to 78 degrees Fahrenheit, salinity close to 34 ppt, a pH between 8.0 and 8.4 and very low nitrates up to 5 ppm with ammonia and nitrite at 0. And, as with a reef, stability of these parameters is as key as the levels themselves. Big swings in temp, salinity or other water parameters can be devastating to all captive marine animals, but particularly to sensitive invertebrates like these cuttles. A mature aquarium with live rock is ideal and, if lighting is adequate, these animals may coexist with non-stinging corals like mushrooms, polyps, soft corals and leathers. Hermit crabs may be used as a clean-up crew but snails and other crabs will definitely be on the menu of these little hunters. Water flow should be moderate; enough to keep the water well aerated but not so strong as to blow these rather delicate creatures around. Filter and pump intakes should be covered with sponge filters to prevent any mishaps. A skimmer is recommended to keep nutrient levels low, increase oxygen saturation in the water and to remove any ink before it can harm the animals. Because these animals are not the escape artists of their octopus cousins, no secure lid is necessary and the cuttles currently in my care are in open-top systems.
Tank size must allow for natural behavior and water stability. It has been noted that too small of a tank, in addition to inciting aggression, can also lead to “butt burn” which is the cuttle bone actually protruding through the mantle tissue as a result of running into the side of the display tank during a sudden jet after being startled. Richard Ross recommends 30 gallons for a single adult animal, 40 gallons for 2, 55 gallons for three and suggests as many as 8 may be housed in a 125 gallon tank. I have been working with these animals in a roughly 50-gallon display that typically houses between 5 and 8 adult S. bandensis with great success. As with most captive marine animals, it may be supposed that increased feeding will result in decreased intraspecies aggression and that may be partly responsible for the success of this rather heavily stocked cuttle display. Nutrient levels are kept in check with 10-20% water changes every 3-4 days. This display relies on live rock, two canister filters and an undergravel filter for it’s filtration and a return pump with loc-line returns for water flow. They are housed with leathers, mushrooms and polyps under power compact lighting with a half-dozen or so small hermits. Water parameters are steady and within the ranges described above. These cuttles have been thriving and actively reproducing in this environment for nearly two years. Additional adults as well as eggs, juviniles and various live foods are housed in a separate large trough and in breeder nets of various sizes therein with the same water parameters as the display. These additional holding areas are essential for the long-term care of a breeding population of S. bandensis.
Dwarf cuttle in holding trough.
Feeding Sepia bandensis is either the funnest part of keeping these animals or the most laborious depending on your disposition and availability. If you fall into the “laborious” category in your approach to feeding your cuttles, you should go ahead and leave this animal to other aquarists who have the time, schedule and patience to meet the feeding requirements of these ravenous little beasts.
I think the shot above shows my little cuttle friends all lined up to be fed. Our electrician, Ryan, is sure he heard one of them say, “you go left and I’ll go right” in an attempt to organize an attack on me and thus secure my hidden stashes of krill and grass shrimp. Regardless of who is correct, these animals definitely recognize that people mean food and they will “beg” at the glass when their keepers come around. Adult S. bandensis will generally not take dead food off the substrate and must be fed either by hand or with a feeding stick. I feed our population of adults a mix of frozen krill soaked in a vitamin and amino acid supplement, extra large frozen mysis, frozen “bait shrimp” and the occasional gut-loaded live grass shrimp.
Enriched krill on a feeding stick.
The adult cuttles are fed twice daily at 8 am and 3 pm. With no real way to tell who has eaten in a larger population such as the one I work with, we simply introduce at least as many pieces of food as we know we have cuttles and rely on their natural survival instincts to drive them to feed. Typically, the food is large enough that each cuttle can only handle and eat one piece at a time which may take minutes, allowing even the more timid animals a chance to grab their share. Below we see one of my little pals taking an enriched krill from a feeding stick. As usual, it grabs the monofilament line for a bit as we play a quick game of interspecies tug-of-war before it finally lets go.
It should be noted that enrichment is essential to keeping highly intelligent animals like Sepia bandensis. The interactions in the feeding video above are great examples of how simple activities like feeding your cuttles or cleaning their quarters can provide valuable stimulation for those little doughnut-shaped brains of theirs. Much more could be said about enrichment for these other and captive animals but we will leave that topic for another day.
In spite of the time involved, feeding adult S. bandensis is a rather simple affair with various frozen whole shrimp foods readily available and easy to store. Feeding the hatchlings and juveniles is a more complicated endeavor and requires live foods and all that providing such foods requires. The S. bandensis keeper with a breeding population will be faced with an array of egg clusters and juveniles at various stages of growth. The eggs are easy to tend to. They should be removed from the display as soon as they are noticed and placed into a holding tank with the same parameters as the display. When the ink-covered eggs are swollen and the babies clearly visible, the eggs should be moved into a breeder net in preparation for hatching. As the babies hatch, they may be moved to another breeder with others from the same clutch where they will receive their first feedings of live mysis. Live mysis and the other frozen and live foods mentioned here are all available through online vendors and may be available in local stores. The babies may not feed for the first week but live mysis should be maintained in the breeder net as soon as the hatchlings are introduced. As the babies grow, they may move on to very small live grass shrimp. Eventually, mature animals reliably ween onto frozen foods presented as described above but exact timelines will vary. Be prepared to offer live foods to your developing baby cuttles for months, not just weeks. This can be costly and take up considerable space and time and is a big factor in whether this animal is a suitable one for captivity for you or your institution. More about housing and feeding baby cuttles as we turn now to breeding these short-lived animals.
In 2006, Richard Ross is thought to have been the first aquarist to breed Sepia bandensis in captivity and to “close the life cycle” in 2007. This animal does not occur naturally near North America and this may be the reason these animals weren’t kept sooner. Also, adults do not ship well and this perhaps contributed to their reputation as difficult to keep. Should you acquire specimens of this species it will likely be as eggs or hatchlings and these ship much better. These animals are also currently bred and maintained at the Seattle Aquarium in Seattle, WA as well as by other public and research institutions and individual hobbyists. Ultimately, it appears keeping and breeding S. bandensis in captivity is not particularly more difficult that maintaining a reef other than the feeding and breeding requirements noted here.
Here are presumably a male and female pair flirting. It’s thought impossible to sex Dwarf Cuttlefish visually though they reportedly recognize each other’s sex on sight.
S. bandensis reaches sexual maturity at about 5 months at if you have at least one male and one female, it’s quite possible you’ll see clusters of 10 to 40 eggs soon thereafter. These animals mate head to head for several minutes during which the male passes his sperm packet to the female. She broods the eggs and lays them in grape-like clusters. She covers each egg with her ink which hides the developing baby and becomes more translucent at the eggs swells and matures.
Swollen S. bandensis eggs with babies clearly visible. The babies will hatch as tiny replicas of their parents.
After the eggs are laid, the cluster should be moved into a breeder net in a holding system with the same parameters as the display tank. As the eggs swell and near hatching, a few live mysis may be added to the breeder net to provide first food for an unnoticed hatchling. Once the babies hatch, they should be moved to another breeder net. A turkey baster may be gently used for this purposed. As the young get larger, they’ll need to be scooped from tank to tank and net to net with a cup. It’s best not to lift their fragile bodies out of water if at all possible. Note, a perturbed juvi can ink, if only a tiny amount. Try not to p*%$ off your baby cuttles too much in the transfer process.
As various groups of babies grow they should be moved through a series of breeder nets, always being kept with individuals of similar size to avoid cannibalism. Quantities of live mysis should be maintained in the breeder nets at all times if possible. These little animals grow fast and first-time keepers will likely be surprised by the number of live mysis they eat. Be prepared and have plenty on hand. Eventually, small and then larger live grass shrimp may be fed. The grass shrimp can be easily gut-loaded prior to feeding with a high-quality pelletized fish food.
Hatchlings and live mysis in a breeder net.
These little cuttles have all the attributes of their adult counterparts; lightening-fast feeding tentacles, amazing agility and the ability to ink and to change colors and patterns.
Eventually, if you’re successful at breeding and raising cuttles, it’s entirely likely you’ll end up with too many. Way to many. It’s good to consider what you’ll do with those little animals before you have to deal with potentially hundreds of Dwarf Cuttlefish. You may be able to donate them to public aquariums, research institutions or other hobbyists. You may be able to sell or give them to a high quality local marine aquarium retailer. Or you may be able to distribute them yourself online. Regardless, this is a big undertaking with much life at stake. All this needs to be considered before getting your first batch of eggs or juvies. Like the intensity of the feeding regimen, this prolific aspect of this species may be either a boon or a bane to its keepers depending on their interest in and capacity to deal with their ever expanding cuttle family.
After about 3-5 months, your little cuttles may be ready to join a population of adults. As with the batches of juveniles, keeping same size adults together will cut down on aggression and cannibalism. As keeping and breeding these animals is still in its infancy, issues of inbreeding haven’t really been explored. Long term maintenance of a breeding population of S. bandensis would likely reveal many new aspects to the life history as well as the captive care and breeding if this amazing and very keepable cephalopod.
After about one year, your adult cuttles will begin to die through a process called senescence which is a gradual loss of faculties ending in the animal’s death. This can take the form refusing to feed or being unable to grasp food with the feeding tentacles. It may also involve parts of arms or other body parts sort of rotting away. Hermit crabs have been observed feeding on a living cuttlefish in senescence and the cuttle appeared entirely unperturbed. This process can be heart-wrenching for an aquarist who has doted on these animals and this should be considered if a captive population of S. bandensis is in your future.
I used the following references in preparing this article as well as my own experiences working with Sepia bandensis in captivity. All photos and video are my own.
I hope this is helpful to anyone considering keeping this species and I thank you for reading.